1. Technical Field
The present invention relates to a pin mirror cutter to machine, for example, a crank shaft used for a reciprocal internal combustion engine, and a throw-away tip (hereinafter referred to as a tip) mounted thereon, and particularly, to an attaching mechanism when a pin mirror cutter is attached to an adaptor mounted on a processing machine.
2. Background Art
Conventionally, for example, a so-called internal pin mirror cutter as disclosed in Japanese Unexamined Patent Application Publication No. 2002-46009 is known.
In this pin mirror cutter, a plurality of first tip mounting seats are formed in an inner peripheral face of a substantially annular cutter body which rotates around the axis, a plurality of second tip mounting seats are formed in opposite end faces of a cutter body, and the same type of tip is mounted on each of the first tip mounting seat and second tip mounting seat.
In the tip, a total of eight cutting edges are formed at the intersecting ridgeline parts between a pair of oppositely disposed side faces of a tip body, which is formed in a substantially parallelogrammic flat-plate shape, and upper and lower faces of the tip body. In a pair of side faces other than the above one pair of side faces, the regions of the tip body on the side of their obtuse corner parts are cut off such that their corner angle is reduced, whereby the other pair of side faces is composed of two wall surfaces to form a crest shape which is made convex toward the outside of the tip body. Furthermore, each of parts connected to the other pair of side faces in the upper and lower faces of the tip body is chamfered in the shape of a convex surface.
The tip mounted on the first tip mounting seat has one cutting edge which is formed in an acute corner part of the tip body which is formed in a substantially parallelogrammic flat-plate shape. This one cutting edge is caused to protrude from an inner peripheral face of the cutter body so as to have a positive axial rake (axial rake angle) and a negative radial rake (radial rake angle) and is used as a pin edge which machines an outer peripheral face of a pin part (shaft part) in a crank shaft.
Moreover, the tip mounted on the second tip mounting seat has one cutting edge formed in an obtuse corner part of the tip body which is formed in a substantially parallelogrammic flat-plate shape. This cutting edge is caused to protrude from an end face of a cutter body so as to have a negative axial rake (axial rake angle) and a negative radial rake (radial rake angle), and is used as a wave edge which machines side faces of a counterweight part in a crank shaft.
In such a pin mirror cutter, by mounting the same type of tip on the first and second tip mounting seats, the cutting edges formed in a total of eight places with one chip can be provided for cutting and thereby the tool cost of the pin mirror cutter can be suppressed. Also, by using a tip having a substantially parallelogrammic flat-plate-shaped tip body including the other pair of side faces as mentioned above, with respect to a tip to be mounted on the first tip mounting seat, a rake angle to be given to a cutting edge used as the pin edge is set to be positive and the cutting resistance is reduced.
Another conventional pin mirror cutter includes a substantially annular adaptor mounted on a processing machine, and a substantially annular cutter body which is attached to an inner peripheral part of this adaptor and rotates around the axis. The cutter body is formed with a substantially annular flange part which protrudes from the entire periphery of an outer peripheral face of the cutter body toward the radial outer periphery, and the adaptor is formed with a substantially annular stepped part which is recessed from the entire periphery of an inner peripheral face of the adaptor toward the radial outer periphery and receives the flange part.
In such a pin mirror cutter, if the cutter body is inserted into the inner peripheral part of the adaptor along the axial direction thereof, the flange part of the cutter body and the stepped parts of the adaptor are brought into surface contact into each other such that they overlap each other along the radial direction of the cutter body, and the cutter body is positioned in its axial direction with respect to the adaptor. Also, a plurality of key members are allowed to fit into a plurality of notched parts which are formed so as to be depressed from the outer peripheral face of the cutter body toward the radial inner periphery, and one end face of the cutter body is pressed by a plurality of clampers. Thereby, the cutter body is fixed to the adaptor in the peripheral direction, the axis of the cutter body is approximately aligned with the axis of the adaptor, and the cutter body is attached to the inner peripheral part of the adaptor.
However, in such a conventional pin mirror cutter, with respect to a substantially annular contact surface where the flange part of the cutter body can be brought into surface contact with the stepped part of the adaptor, the radial length of the cutter body is set longer, and one end face of the cutter body is pressed by the plurality of clampers. However, the cutter is too weak against a large load (load in the axial direction of the cutter body) in a thrust direction. That is, as a load in the thrust direction is applied to the cutter with the cutter body attached to the adaptor, the stepped part of the cutter body or the flange part of the adaptor may be bent, and correspondingly, a deviation in the thrust direction (axial direction of the cutter body) with respect to the adaptor may be caused. Therefore, the deflection precision of the plurality of cutting edges provided in the inner peripheral part of the cutter body deteriorates.
Moreover, Japanese Unexamined Patent Application Publication No. 8-118125 discloses a pin mirror cutter in which a cutter body is formed with a plurality of protruding parts which protrude from the outer peripheral face of the cutter body toward the radial outer periphery, an adaptor is formed with a plurality of notched parts are recessed from the inner peripheral face of the adaptor toward the radial outer periphery for allowing the plurality of protruding parts to fit thereinto, and each of the plurality of protruding parts and the plurality of notched parts is formed in a tapered shape such that the distance between a pair of side faces which face a peripheral direction becomes small as it goes to the front side in a cutter insertion direction (the direction when the cutter body is inserted into an inner peripheral part of the adaptor).
In such a pin mirror cutter, when the cutter body is inserted into the inner peripheral part of the adaptor along the axial direction, the plurality of protruding parts of the cutter body are fitted into the plurality of notched parts, respectively, of the adaptor, whereby the cutter body is positioned in the axial direction with respect to the adaptor, the cutter body is fixed to the adaptor in the peripheral direction, and the axis of the cutter body is approximately aligned with the axis of the adaptor. Also, one end face of the cutter body is pressed by a plurality of dampers and thereby the cutter body is attached to the inner peripheral part of the adaptor.
Yet another conventional pin mirror cutter includes a substantially annular adaptor mounted on a processing machine, and a substantially annular cutter body which is attached to an inner peripheral part of this adaptor and rotates around an axis. For example, Japanese Unexamined Patent Application Publication No. 8-118125 discloses a pin mirror cutter in which a cutter body is formed with a plurality of protruding parts which protrude from the outer peripheral face of the cutter body toward the radial outer periphery, an adaptor is formed with a plurality of notched parts which are recessed from the inner peripheral face of the adaptor toward the radial outer periphery for allowing the plurality of protruding parts to fit thereinto, and each of the plurality of protruding parts and the plurality of notched parts is formed in a tapered shape such that the distance between a pair of side faces which face a peripheral direction becomes small as it goes to the front side in a cutter insertion direction (the direction when the cutter body is inserted into an inner peripheral part of the adaptor).
In such a pin mirror cutter, when the cutter body is inserted into the inner peripheral part of the adaptor along the axial direction, the plurality of protruding parts of the cutter body are fitted into the plurality of notched parts, respectively, of the adaptor, whereby the cutter body is positioned in the axial direction with respect to the adaptor, the cutter body is fixed to the adaptor in the peripheral direction, and the axis of the cutter body is approximately aligned with the axis of the adaptor. Also, one end face of the cutter body is pressed by a plurality of dampers and thereby the cutter body is attached to the inner peripheral part of the adaptor.
However, in the pin mirror cutter disclosed in Japanese Unexamined Patent Application Publication No. 2002-46009, the cutting edge as a pin edge whose axial rake is set to be positive is formed in the acute corner part of the tip body which is formed in a substantially parallelogrammic flat-plate shape, and this tip body includes the other pair of side faces which are cut off in the region on the side of the obtuse corner part. Thus, the radial rake of the cutting edge as a wave edge formed in the obtuse corner part of the tip body may become very large inevitably toward the negative angle. Therefore, the pin mirror cutter disclosed in this Japanese Unexamined Patent Application Publication No. 2002-46009 could not be effective solving means for reducing cutting resistance in actuality.
Moreover, since the tip body of such a tip includes the other pair of side faces which are cut off at the obtuse corner part, if the tip body is not lengthened by that cut-off, the cutting edge length could not be sufficiently ensured. Therefore, the occupation space of the tip mounting seat to be formed in the cutter body may become large, and the strength of this cutter body may be lowered. In addition, since the shape of the tip body is complicated, there is also a problem in that the manufacture is difficult and the processing cost may increase.